The arc Pacheho does is in trade as Ultimate Avengers: The Next Generation. It's fairly late on, but not a bad jumping on point. It's... Millar-y in places, though, especially issue 5. On the other hand, it focuses on Steve and gives a decent insight into his brain, which is... actually rather scary. (It also introduces Tony's twin Gregory.)

Also, warning, the Ultimate Captain America miniseries may tempt you. It has some glorious art. But it is poison and terrible and the characterisation of Cap is shamefully bad, and actively contradicts much other characterisation. If anyone tries to foist it upon you, kick them inna fork and run.